// Copyright 2004-2010 Castle Project - http://www.castleproject.org/
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//     http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

namespace Fas.Tem.Runtime.Parser
{
    /// <summary> 
    /// This interface describes a character stream that maintains line and
    /// column number positions of the characters.  It also has the capability
    /// to backup the stream to some extent.  An implementation of this
    /// interface is used in the TokenManager implementation generated by
    /// JavaCCParser.
    ///
    /// All the methods except backup can be implemented in any fashion. backup
    /// needs to be implemented correctly for the correct operation of the lexer.
    /// Rest of the methods are all used to get information like line number,
    /// column number and the String that constitutes a token and are not used
    /// by the lexer. Hence their implementation won't affect the generated lexer's
    /// operation.
    /// </summary>
    public interface ICharStream
    {
        /// <summary>
        /// The currenct character.
        /// </summary>
        char CurrentCharacter { get; }

        /// <summary> Returns the next character from the selected input.  The method
        /// of selecting the input is the responsibility of the class
        /// implementing this interface.  Can throw any java.io.IOException.
        /// </summary>
        bool ReadChar();

        /// <summary> Backs up the input stream by amount steps. Lexer calls this method if it
        /// had already read some characters, but could not use them to match a
        /// (longer) token. So, they will be used again as the prefix of the next
        /// token and it is the implemetation's responsibility to do this right.
        /// </summary>
        void Backup(int amount);

        /// <summary> Returns the next character that marks the beginning of the next token.
        /// All characters must remain in the buffer between two successive calls
        /// to this method to implement backup correctly.
        /// </summary>
        bool BeginToken();

        /// <summary> Returns a string made up of characters from the marked token beginning
        /// to the current buffer position. Implementations have the choice of returning
        /// anything that they want to. For example, for efficiency, one might decide
        /// to just return null, which is a valid implementation.
        /// </summary>
        string GetImage();

        /// <summary> 
        /// Returns an array of characters that make up the suffix of length 'len' for
        /// the currently matched token. This is used to build up the matched string
        /// for use in actions in the case of MORE. A simple and inefficient
        /// implementation of this is as follows :
        ///
        /// {
        /// String t = GetImage();
        /// return t.substring(t.length() - len, t.length()).toCharArray();
        /// }
        /// </summary>
        char[] GetSuffix(int len);

        /// <summary> The lexer calls this function to indicate that it is done with the stream
        /// and hence implementations can free any resources held by this class.
        /// Again, the body of this function can be just empty and it will not
        /// affect the lexer's operation.
        /// </summary>
        void Done();

        /// <summary>
        /// Gets the column.
        /// </summary>
        /// <value>The column.</value>
        int Column { get; }

        /// <summary>
        /// Gets the line.
        /// </summary>
        /// <value>The line.</value>
        int Line { get; }

        /// <summary>
        /// Gets the end column.
        /// </summary>
        /// <value>The end column.</value>
        int EndColumn { get; }

        /// <summary>
        /// Gets the end line.
        /// </summary>
        /// <value>The end line.</value>
        int EndLine { get; }

        /// <summary>
        /// Gets the begin column.
        /// </summary>
        /// <value>The begin column.</value>
        int BeginColumn { get; }

        /// <summary>
        /// Gets the begin line.
        /// </summary>
        /// <value>The begin line.</value>
        int BeginLine { get; }
    }
}